The present invention is related generally to the field of orthodontics. Particularly, the present invention is related to methods, systems and devices involving split dental molds. More particularly, the present invention involves dental molds having tooth portions and oral soft tissue portions of different types.
Traditional methods of dental mold making are well known, such as those described in Graber, Orthodontics: Principle and Practice, Second Edition, Saunders, Philadelphia, 1969, pp. 401-415. Typically, these methods involve forming an impression of the patent""s dentition using a suitable impression material, such as alginate or polyvinylsiloxane (PVS). Impressions of the upper jaw typically include the teeth, the palate and gingival tissue surrounding the teeth on the facial and lingual surfaces. Impressions of the lower jaw typically include the teeth and gingival tissue surrounding the teeth on the facial and lingual surfaces. Plaster is then poured into the impression to form a relief of the dental features. The relief is a permanent, three-dimensional mold of the dentition and oral tissues.
Improved methods of mold making include rapid prototyping. Rapid prototyping is a technology which has developed in the last decade. Through the use of modern solid modeling CAD packages, combined with laser systems and new materials, solid parts may now be generated directly from a computer model. Examples of this technology include stereolithography (SLA), laminate object manufacturing (LOM), and fused deposition modeling (FDM), to name a few.
Stereolithography is a method that employs an ultraviolet laser to cure a thin layer of liquid plastic into a solid. The process operates by taking a thin layer of the light-sensitive liquid plastic and passing the laser beam over the points where the part is solid. Once a pass is completed, another layer of the liquid is added to the existing part, and the process repeats until the full part height is achieved. SLA parts are extremely accurate, and tend to have excellent surface finishes. A variety of SLA materials are available for different purposes, including waxes, plastics, and flexible elastomers.
Laminate object manufacturing builds a part by taking individual sheets of paper that have a layer of glue on one side and building up successive sections of a part. As each layer is laid down, a laser beam passes over the edges of the part, detailing the part and separating the part from the excess material. In addition, the laser beam creates a grid throughout the excess material. After the final sheet is laid down, the part may be separated from the excess material by removing cubes of the grid in a systematic fashion. LOM parts are accurate, and very easy to sand and paint. LOM parts also have different strengths in different directions due to the paper layers.
Fused deposition modeling is a process that most closely resembles a miniature glue gun. In fused deposition modeling, a heat softening and curing plastic is melted in a small nozzle which puts down a very fine bead wherever the solid part is supposed to be. FDM parts have a rougher surface finish than an SLA part, but typically are stronger and more durable. In all cases, parts created by rapid prototyping methods are generated relatively quickly and are accurate to a few thousandths of an inch.
Producing a dental mold with rapid prototyping methods requires the use of a computerized model or digital data set representing the dental geometry and tooth configuration. The model is used to guide the mold making process to produce a replica or relief of the computerized model. The resulting relief is a three-dimensional mold of the dentition. This method of making dental molds is particularly applicable to situations in which multiple molds are needed to be produced. In this case, one computerized model may be used to make a number of molds in an automated fashion. In addition, this method is applicable to situations in which a mold of a tooth arrangement which differs from the patient""s current tooth arrangement is needed to be produced or molds of multiple tooth arrangements which differ from each other and the patient need to be produced. In either case, the computerized model of the patient""s teeth may be manipulated to portray each new tooth arrangement and a mold may be produced to reflect each successive arrangement. This may be repeated any number of times to derive a number of molds with differing tooth arrangements. Such techniques may speed production time and reduce costs by eliminating the need for repeated casting and artistic resetting of teeth in traditional mold manufacturing.
Series of dental molds, such as those described above, may be used in the generation of elastic repositioning appliances for a new type of orthodontic treatment being developed by Align Technology, Inc., Santa Clara, Calif., assignee of the present application. Such appliances are generated by thermoforming a thin sheet of elastic material over a mold of a desired tooth arrangement to form a shell. The shell of the desired tooth arrangement generally conforms to a patient""s teeth but is slightly out of alignment with the initial tooth configuration. Placement of the elastic positioner over the teeth applies controlled forces in specific locations to gradually move the teeth into the desired configuration. Repetition of this process with successive appliances comprising new configurations eventually moves the teeth through a series of intermediate configurations to a final desired configuration. A full description of an exemplary elastic polymeric positioning appliance is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596 which designates the United States and which is assigned to the assignee of the present invention. Both documents are incorporated by reference for all purposes.
To carry out such orthodontic treatment, a series of computer models or digital data sets will be generated, stored and utilized to fabricate a series of representative dental molds. Typically, only the digital information related to the tooth arrangement will be stored due to cost and space limitations. However, to form a properly fitting elastic repositioning appliance or other dental appliance, it will at times be necessary to include in the mold a patient""s oral soft tissue, such as a palate, facial gingival tissue and/or lingual gingival tissue. This may be the case when adding accessories to a basic elastic repositioning shell, such as palatal bars, lingual flanges, lingual pads, buccal shields, buccinator bows or wire shields, a full description of which is described in U.S. Provisional Patent Application No. 60/199649, filed Apr. 25, 2000, and the full disclosure is hereby incorporated by reference for all purposes. These accessories may contact or interact with portions of the soft tissue requiring a mold of such tissues to properly position the accessory in or on the appliance. In addition, this may be the case when producing traditional orthodontic retainers and positioners. Traditional appliances may be used as part of an orthodontic treatment plan utilizing elastic repositioning appliances, particularly in the final stages of treatment. During such stages, for example, any residual intrusion of the teeth due to the presence of elastic appliances may be corrected with the use of a traditional retainer. Such retainers typically comprise a polymeric replica of the palate or portions of the gingiva which support metal wires which wrap around the perimeter of the teeth.
Generating dental molds including both the tooth arrangement and the geometry of the oral soft tissue of a patient for each stage of treatment throughout orthodontic treatment is, however, expensive, due to cost of materials, fabrication time and space required for storage of digital information. Likewise, generating such a mold during treatment as necessary is also expensive due to 1) the added space required to store the additional digital information of the oral soft tissue, and 2) the time and labor required to manipulate the digital information to join a given tooth arrangement with an oral soft tissue geometry each time a mold is desired to be produced.
Therefore, improved devices, systems and methods are desired to design and fabricate dental molds suitable for the production of elastic repositioning appliances and other dental appliances which require structure corresponding to a patient""s oral soft tissue. Such dental molds should provide an oral soft tissue relief or mold replicating the oral soft tissues of the patient and a relief of the desired tooth configuration, whether the configuration be the patient""s current tooth configuration or a new tooth configuration desired in orthodontic treatment. Such dental molds should be economical, and in particular should reduce the cost of materials, fabrication time and labor, and space required for storage of digital information. At least some of these objectives will be met by the present invention described hereinafter.
The present invention provides improved devices, systems and methods for producing dental molds, each having portions representing a patient""s oral soft tissue and a desired tooth configuration. These molds are designed for use in the fabrication of appliances used in orthodontic treatment, particularly, elastic repositioning appliances. However, they may also be used in the fabrication of traditional appliances, such as retainers and positioners, used, for example in the final or finishing stages of an otherwise conventional treatment. The dental molds are comprised of a mold or relief of the patient""s soft tissue, such as a palate, facial gingival tissue and/or lingual gingival tissue, and a separate or separable mold or relief of the patient""s dental arch having teeth in a desired tooth configuration. Since, the tooth configuration will change as a patient progresses through orthodontic treatment, the relief of the dental arch will be fabricated separately from the relief of the oral soft tissue. Typically, the dental arch relief will be fabricated using rapid prototyping methods. The soft tissue relief may also be fabricated using rapid prototyping, however it may also be fabricated using traditional mold making methods, i.e., casting with plaster or other mold making materials. In either case, the resulting dental mold with be comprised of a xe2x80x9csplit-moldxe2x80x9d having fixedly or removably joined arch and soft tissue reliefs.
When a patient is treated with elastic repositioning appliances, a series of such appliances are produced to gradually reposition the patient""s teeth from an initial tooth configuration, through a series of intermediate tooth configurations, to a final or other targeted tooth configuration. To accomplish this, the patient""s initial tooth arrangement and shape of the patient""s dental arch are represented by a digital data set in a computerized model. The data set is then manipulated to reflect progressive tooth arrangements. For each arrangement, the data is used to guide computerized model fabrication systems, or rapid prototyping systems, to create a corresponding three-dimensional mold or relief. As described above, such systems may include stereolithography (SLA), laminate object manufacturing (LOM), and fused deposition modeling (FDM), to name a few. Due to the methodology of rapid prototyping systems, the resulting relief is typically comprised of fused layers of material, such as wax, plastic, flexible elastomers or paper.
At a given point in treatment, it may be necessary to produce an appliance which requires a mold having the oral soft tissue features of the patient. Since the majority of the soft tissue areas remain unchanged throughout orthodontic treatment, it is not necessary to use computerized models or rapid prototyping methods to generate a relief of the patient""s soft tissue features. One may simply rely on the oral features of the patient prior to treatment or at the present time and traditional mold making methods using plaster casting, for example. This may eliminate the need to create and store a digital data set representing the soft tissue and, consequently, the added time and labor to manipulate the data sets to join the soft tissue with the dental arch in the computerized model. The resulting split or composite mold will then usually be comprised of a plaster relief of the patient""s oral soft tissue and a fused layered relief of the patient""s dental arch having a tooth arrangement reflecting a future stage in the orthodontic treatment protocol. The split mold may then be used to produce the desired appliance.
Split molds of the present invention may be comprised of a number of designs and may be fabricated using a number of methods. In a first aspect of the present invention, a split mold of an upper or lower jaw of a patient may be comprised of a dental arch relief and an oral soft tissue relief, formed separately from the dental arch relief, wherein the two reliefs are fixedly joined together to anatomically resemble the jaw of the patient. This may be achieved by a number of methods. In an exemplary method, an impression or other cavity mold of the patient""s jaw is produced by traditional methods, such as pressing a dental molding material against the dental features to form depressions or contours corresponding to the teeth and oral features. An SLA model of the desired tooth arrangement (without the majority of the soft tissue features) is also generated to provide the dental arch relief. However, it may be appreciated that the dental arch relief may be fabricated by any known method. The dental arch relief is then positioned in the impression so that contours of the arch relief generally correspond to corresponding contours of the impression or cavity mold. Since the arch relief will likely resemble a future tooth arrangement, the contours of the arch relief may not exactly fit the contours of the impression. However, the differences may be overcome by the flexibility of the impression. With the dental arch relief inserted, the exposed remainder of the impression represents the soft tissue. A mold of the soft tissue may be produced by at least partially filling the remainder of the impression with molding material. Preferred molding materials include, but are not limited to, plaster, urethane, silicone, epoxy and wax. The molding material will flow to fill in exposed areas around the tooth members and will form a relief of the soft tissue. After the material has cured, the fixedly joined reliefs may be removed from the impression. The resulting split-mold may then be used to produce a dental appliance requiring the presence of teeth and soft tissue features.
In a second aspect of the present invention, a split or composite mold of an upper or lower jaw of a patient may be comprised of a dental arch relief and an oral soft tissue relief, formed separately from the dental arch relief, wherein the two reliefs are separably or removably joined together to anatomically resemble the jaw of the patient. In a preferred embodiment, the oral soft tissue relief may be comprised of a portion or portions of the patient""s gingival anatomy with vacant space(s) in the area of the dental arch. For example, the oral soft tissue relief may be comprised of a mold of a palate and facial gingival tissue wherein a vacant arch shaped xe2x80x9ccutoutxe2x80x9d exists between the palate and the facial gingiva. A dental arch relief having a first tooth configuration may then be inserted into the arch shaped cutout to fill the vacant space. In particular, the dental arch relief will have a bottom or base which is configured to mate with the cutout in the palate and facial mold, and the present invention includes systems which comprise a plurality of dental arch reliefs (usually having different tooth arrangements) which may be interchangeably mounted into the palate and facial mold. The result is a corporate structure which anatomically resembles the jaw of the patient having a first tooth configuration. The dental arch relief may then be removed and a different dental arch relief having a second tooth configuration may be inserted. The result would be a corporate structure which anatomically resembles the jaw of the patient having the second tooth configuration. This may be repeated with any number of dental arch reliefs. Thus, the soft tissue relief may remain constant or act as a xe2x80x9cuniversalxe2x80x9d soft tissue mold, while the dental arch reliefs may be interchangeable to represent different configurations. It may be appreciated that the soft tissue relief may simply comprise a portion of the soft tissue, such as the palate or a lingual gingival surface, which may join with the arch relief in at one or more specific locations. For example, the soft tissue relief may join or attach to the side of the arch relief so that the arch relief is not specifically inserted into the soft tissue relief.
The dental arch relief is typically generated by rapid prototyping methods, as described above, such as SLA, LOM, and FDM. Consequently, the relief is often comprised of fused layers of waxes, plastics, flexible elastomers or paper. In addition, the relief may be painted or coated to provide desired surface characteristics. Although the dental arch relief is primarily comprised of tooth members, the gingiva surrounding the tooth members may also be represented. This may be necessary because the gingiva in contact with or near the tooth members may vary with the tooth configurations. Therefore, it may not be feasible to include this in the soft tissue relief and may be provided by the dental arch relief.
The oral soft tissue relief is typically generated by traditional mold making methods. This may involve forming an impression of the patient""s jaw using a suitable impression material, such as alginate or polyvinylsiloxane (PVS). Usually, this will include both the teeth and the oral soft tissues to ensure complete coverage. Plaster or other material may be poured into the impression to form a relief of the dental features. Upon removal of the mold from the impression, the mold may then be modified for use. The mold may be cut or trimmed to isolate a desired portion of the oral soft tissue relief. For example, the dental arch may be removed from the mold, leaving the relief of the palate and facial gingival surfaces intact. In this case, the mold may appear as an oral soft tissue relief having an arch-shaped hole or vacant space in place of the teeth. Thus, a dental arch relief, described above, may be inserted through the arch-shaped hole and held in place. The result may be a split-mold which anatomically resembles the jaw of the patient and may be used to produce a properly fitting appliance.
Similarly, other portions of the mold may be removed leaving portions of the soft tissue relief intact. For example, the lingual gingival surfaces of a lower jaw mold may be cut and isolated for use. In this case, the gingival surfaces or soft tissue relief may be joined with a dental arch relief by placing them in close proximity, snapping them together, bonding them together or joining them by any suitable method. Again, the result may be a split-mold which anatomically resembles portions of the jaw of the patient and may be used to produce a properly fitting appliance. For some appliances, this may be accomplished by heating a thermoformable polymer material and applying vacuum or pressure to form the polymer to the mold. An accessory, such as a lingual pad, may be formed in the appliance which contacts or interacts with the patient""s lingual gingival surfaces.
The oral soft tissue relief may also be generated by rapid prototyping methods, as described above, such as SLA, LOM, and FDM. In this case, a digital data set may be created representing the oral soft tissue. The data set may be used to guide the computerized model fabrication systems to create a corresponding three-dimensional mold or relief. Since the data set may be modified prior to model fabrication, the resulting oral soft tissue relief may be generated in a usable form. Otherwise, the relief may be modified by manual methods so isolate the desired portion of the relief. In any case, the oral soft tissue relief may then be joined with a dental arch relief by placing them in close proximity, snapping them together, bonding them together or joining them by any suitable method. Again, the result may be a split-mold which anatomically resembles portions of the jaw of the patient and may be used to produce a properly fitting appliance. Although the reliefs may be comprised of the same material generated by the same methods, the advantages of the split-mold design are still available. The dental arch relief having a first tooth configuration may be removed and a dental arch relief having a second tooth configuration may be joined to the oral soft tissue relief. And, this may be repeated with third, fourth, fifth, and more tooth configurations. In addition, the digital data set may be used only once to fabricate a xe2x80x9cuniversalxe2x80x9d oral soft tissue relief. This may eliminate time and labor associated with manipulating the data sets to join the dental arch and the gingival tissues in the computer model at various times throughout the treatment. In addition, the digital data set representing the oral soft tissue may be deleted once the oral soft tissue relief is fabricated. This may eliminate the need for additional storage space.
Other objects and advantages of the present invention will become apparent from the detailed description to follow, together with the accompanying drawings.